Article transport apparatuses are known in which control means selects an article transporting vehicle for a transport operation, from among a plurality of article transporting vehicles, based on transport request data that specify an article transferring location for collecting and an article transferring location for delivering from among a plurality of article transferring locations, and then runs the article transporting vehicle that has been selected for the transport operation to the article transferring location for collecting and to the article transferring location for delivering.
Such article transport apparatuses are employed in automated warehouse, for example. The control means selects an article transporting vehicle for a transport operation based on transport request data that are processed in sequence, and then runs the article transporting vehicle selected for the transport operation to an article transferring location for collecting and to an article transferring location for delivering, transporting articles between a plurality of article transferring locations by repeatedly performing a transport operation to transport an article from an article transferring location for collecting to an article transferring location for delivering using any one of the plurality of article transporting vehicles each time transport request data are processed.
Some such article transport apparatuses are provided with two article transporting vehicles and are designed such that the control means controls the operation of the two article transporting vehicles while preventing a collision between them (see JP 2002-175117A, for example).
As in the article transport apparatus detailed in the above patent document, conventionally, control means serves as the mechanism for selecting an article transporting vehicle for a transport operation from among the two article transporting vehicles based on transport request data, and here the control means selects the article transporting vehicle, of the two article transporting vehicles, that is positioned nearer the article transferring location for collecting as the article transporting vehicle for the transport operation.
More specifically, as shown in FIG. 1, a plurality of stations 1 serving as article transferring locations are provided in the lengthwise direction of a path 2 with a spacing between them, and two article handling vehicles 3, that is, a first article handling vehicle 3a and a second article handling vehicle 3b, are provided as article transporting vehicles.
The plurality of stations 1 include a combination of delivery stations 1a provided with a delivery conveyer for transporting articles 20 that are to be delivered from article storage racks 19 of an automated storage facility, stocking stations 1b provided with a stocking conveyer for transporting the articles 20 that are to be stocked in the article storage racks 19 of the automated storage facility, reception stations 1c provided with a reception conveyer for transporting the articles 20 that are to be received from the outside, shipping stations 1d provided with a shipping conveyer for transporting the articles 20 that are to be shipped to the outside, and processing stations 1e for performing processing such as stacking or picking up the articles 20.
The control means for controlling the operation of the two article handling vehicles 3 is configured so as to select the article handling vehicle 3, of the two article transporting vehicles 3, that is positioned closer to the station for collection 1 as the article transporting vehicle 3 for the transport operation, based on the transport request data.
In the conventional article transport apparatus described above, the control means selects the article handling vehicle 3, of the two article transporting vehicles 3, that is located closer to the station for collection 1 as the article transporting vehicle 3 for the transport operation when transport request data are processed, and thus the same article transporting vehicle may be repeatedly selected as the article transporting vehicle for a transport operation.
Accordingly, there is a possibility that the transport operation can be performed by only some article transporting vehicles, even through a plurality of article transporting vehicles have been provided, and this may keep the transport capacity from being improved.
Further description is made using FIG. 1. For example, there is a period during which the task of stocking the articles 20 that have been delivered from the outside into the article storage racks 19 of the automated storage facility is concentrated, and during this period, the transport request data processed for the current transport operation and the transport request data processed for the previous transport operation will specify the same reception station 1c as the station for collection.
The reception station 1c is disposed closer to the second article handling vehicle 3b than the first article handling vehicle 3a, and thus when the control means selects the article handling vehicle that is positioned closer to the station for collection than the other article transporting vehicle as the article transporting vehicle for the transport operation, the second article handling vehicle 3b is repeatedly selected as the article transporting vehicle for the transport operation.
Accordingly, the transport operation is repeatedly performed using the second article handling vehicle 3b, and because only the second article handling vehicle 3b, of the first article handling vehicle 3a and the second article handling vehicle 3b, can be used to perform the transport operation, the transport capacity cannot be increased.